I have only changed origin_type, but if we are using tarball loader, then I suppose we have to change this according to that

Yes, but there is no need for another code change

In swh-lister, my understanding of the current code is that now the task-type will change to load-tar.
Thus the migration i hinted at yesterday in irc.

13:36:01 +ardumont | archit_agrawal[m: could you change the lister-gnu's origin-type from gnu to tar btw?
13:36:38 +ardumont | it will also change the scheduler's task type from load-gnu to load-tar but i'll deal with 
                     that part later (impact is in the scheduler)
13:36:54 +ardumont | (as the output tasks do not load yet, that's not an issue)

For the loader-tar in question, indeed, currently it does not support the contract.
But that will be part of the refactoring of the other task i mentioned in irc in regards to the "distribution" or "package" loader (T1389).

As this runs in production, I need to:

• migrate the actual data in swh-lister's db

update gnu_repo set origin_type='tar' where origin_type='gnu';

• migrate the scheduler's data

From the top of my head:

# insert new task-type 'load-tar' (which does not exist yet IIRC)
insert into task_type(name, ...) values ('load-tar'...); # or some such
update task set task_type='load-tar' where task_type='load-gnu';
delete from task_type where task_type='load-gnu';